Apparatus for measuring breath volume



May 16, 1967 J. ARP ET AL 3,319,624

APPARATUS FOR MEASURING BREATH VOLUME Filed Jan. 15, 1964 SACK Z5COLLAPSING SOLENOID VOLUME/ W MEASURING SYRINE' '1 FLOP I .SCHMITTTRIGGER mmszn 5i p? FOLLOWER SYR/NGE I SOLENOID SCIMTT TRIGGER INVENTORS VALVE d. LEON AEP RONALD u. GRIFFITH United States Patent ()fl3,319,624 Patented May 16:, 1967 3,319,624 APPARATUS FOR MEASURHIGBREATH VOLUME Leon J. Arp, Ames, Iowa, and Ronald J. Griflith,Morristown, N.J., assignors to Iowa State University ResearchFoundation, Inc., Ames, Iowa, a corporation of Iowa Filed Jan. 15, 1964,Ser. No. 337,778

' Claims. (Cl. 1282.08)

This invention relates to apparatus for measuring breath yolume, and,more particularly, relates to apparatus for performing this functionrelative to an infant.

Respiratory difiiculties are not unusual with infants, particularlypremature babies. It is, therefore, essential that some augmentation ofthe natural breathing faculty be provided, and, as an incident to this,it is necessary to .know the tidal volume. It is with the latterdeterminacernpanying drawing, in which:

FIG. 1 is a schematic representation of an elevational view, partiallyin section, of apparatus which serves to determine the volume of aselected exhaled breath of an infant; and

FIG. 2 is a schematic representation of electrical circuitry associatedwith the electromechanical components of FIG. 1.

In the illustration given, and with particular reference to FIG. 1, thevolumetric portion of the apparatus is seen in semi-schematic formwherein the numeral 10 designates a nose mask adapted to be connected toan infant (not shown). Suitable for this purpose is the nose maskdescribed in the copending, co-owned application of John B. Buck, SerialNo. 351,182, filed March 11, 1964, and reference to that application maybe made for additional details. The nose mask fits closely about thenose of the infant, minimizing dead space, yet permits the mouth to beexposed for feeding, vomiting, mucous extraction, etc. The neonatalinfant normally breathes through his nose, so that the mouth covering isunnecessary as well as being undesirable.

It will be seen that the mask 11) is coupled to the conduits 11 and 12,the conduit 12 serving to provide a flow passage for inhaled air, asdesignated by the arrow marked 13. Air at 13 enters the conduit 12 andpasses through a check valve designated 14 and thence through a triggermechanism generally designated 15. The trigger mechanism includes athermistor 15 sensitive to air movement. The thermistor 16, whenenergized, is employed to operate a rotary valve 17. In the position ofthe valve spool 18 seen in FIG. 1, the exhalation conduit 11 iscommunicated to the atmosphere via the flow passage 19. Flow in theexhalation conduit 11 is permitted in only one direction by virtue of acheck valve utilizing a thin silicone rubber valve diaphragm 21.

With the appearance of a signal from the trigger mechanism 15, therotatable valve spool 18 of the valve 17 is positioned to couple theexhalation conduit 11 to a collapsible sack device generally designated22. Thus, as the patient exhales, air flows through the check valve 20and the rotary valve 17 into the collapsible collection sack structure22. All of the exhaled air is at this time contained in the sackstructure 22, and when the patient next inhales, the trigger mechanism15 delivers another electrical pulse to the electrical circuitry shownin FIG. 2. The pulse so delivered causes the rotary valve element 18 toreturn to the by-pass position (venting the exhalation conduit 11 toatmosphere as at 19) and energizes the solenoid 23 for collapsing thesack 24 provided as part of the sack structure 22. For this purpose, thesolenoid armature is equipped with a platen 25 which is retractable" toforce the sack 24 into a flattened or collapsed condition against thesack structure base 22a. The sack in the illustration given isconstructed of 0.002" thick rubber and possesses essentially noresilency in the range of volumes encountered-the infant breathingvolume being of the order of 5-20 cc.

The exhaled breath from the sack 24 is forced there from by the actionof the platen 25 into a glass syringe generally designated 26. For thispurpose, a tube as at 27 is provided to couple the sack 24 with thebarrel 28 of the syringe 26. The syringe piston 29 rises appropriatelyto indicate the exhaled 'volume. Here, it will be appreciated that thesolenoid 23 is providing the work necessary to elevate the syringepiston 29. The problem in the past in respiration :meters has been tomeasure accurately small volumes of breath without having the infantwork against a back pressure of resistance. This is achieved in theinstant invention by breathing into the sack 24, which is constructed ofrelatively thin rubber, and then letting the platen 25 do the work ofraising the syringe piston 29. To substantially eliminate any error dueto compression by virtue of acting as a syringe piston 29, the piston 29is counterbalanced by weight 30 to a suitable pulley system generallydesignated 31. Thus, the displacement of the syringe piston 29 isdirectly proportional to the volume of air forced into it from thecollection sack 24. As the syringe piston 29 rises, the string 32 of thepulley system passes over an idler pulley 33 and around a pulley 34attached to a linear potentiometer schematically represented anddesignated 35. The output of the potentiometer 35 is delivered to ameter 36 for a direct read-out of the volume of the air exhaled by thepatient. Alternatively or cumulatively, the read-out can be achievedthrough an optical system embodying a light source 38, a lens 39, and aprojection screen 40 all associated with the syringe barrel 28.

The system is returned to ready condition by mechanically forcing thesyringe piston downwardly by a solenoid-actuated pull-down arm 41 andopening the exhaust valve 42 for the exhaust of the air in the syringe26. After this has been achieved and the valve 42 returned to the closedcondition, the solenoid 2 3 is deenen gized to return the platen 25 tothe position seen in FIG. 1.

The solenoids for pulling down the syringe piston 29 and for operatingthe exhaust valve 42 are represented schematically in the diagram ofFIG. 2 as at 43 and 43'. Ganged switches 44 and 45 (normally closed andnormally open, respectively) are operated by the displacement of thesyringe piston 29 and a normally open switch 46 is closed when theplaten 25 is moved so as to collapse the sack 24. Voltage is applied atthe three points designated V in FIG. 2 and three Eccles-Jordan orflip-flop circuits 47, 48 and 49 are also provided, as seen in FIG. 2.The primary flip-flop circuit used in operating the apparatus of FIG. 1is designated 49 and is seen to be electrically coupled to the triggermechanism 15 by means of an amplifier 50, a Schmitt trigger 51,capacitor 52, emitter follower 53, and an And gate 54. The initialcondition of the flip-flop 49 is such as to deliver output current to apower amplifier 55 and thence to a suitable solenoid actuator 56operably associated with the rotary.

valve element 18 when the Read switch 57 is closed temporarily.

Closing the normally open switch 57 changes the condition of flip-flopcircuit 48 to make the And gate 54 conductive as soon as a signal fromthe emitter follower 53 is presented to the And gate 54. When the Andgate 54 simultaneously has a signal presented at both of its inputs, anoutput signal is delivered to the primary flip-flop circuit 49, thuschanging the condition of flip-flop 49 from its start position.

The output signal from flip-flop 49 is amplified by 55 to cause theactuation of the rotary valve 17 by the electromechanical actuator 56.At this time the infant breathes out and into the rubber collection sack24.

As the infant again inhales, the trigger mechanism '15 delivers a pulsethrough the circuits 50, 51, 52, 53

and 54 to change the flip-flop circuit 49 back to its start position.Having removed the signal from the amplifier 55, the rotary valve spool18 returns to its initial by-pass condition seen in FIG. 1.

The capacitor 53 then passes a feed-back signal from the flip-flop 49 toflip-flop 48, thus causing the latter to return to its start condition.When the flip-flop 48 returns to its start condition, one of the inputsignals is removed from the And gate 49. .This prevents the switching ofthe flip-flop 49 by signals generated by the circuits 15, 50, 51 and 52while the infant breathes during the remainder of the measuring process.Capacitor 58 also passes current to the flip-flop 47, causingapplication of power via the amplifier 59 to the platen solenoid 23.This causes the platen 25 to be retracted for collapsing the sack 24.The completion of this collapsing movement closes the normally openswitch 46 and applies current through a delay system 69, a Schmitttrigger 61, and a power amplifier 62 to the pull-down solenoids 43 and43. Interposed between the power amplifier 62 and the solenoids 43 and43' is the normally open switch 45 which is closed upon initial upwardmovement of the piston 29. The delay system 60 is suitably constitutedto provide sufiicient time for reading the meter 36 by the technician orthe medical personnel attending the operation of the apparatus.

Upon actuation of the pulldown solenoid mechanism 43, the syringe piston29 is returned to its bottom dead center position which coincidentallycloses the switch 44, applying a dilferent signal via the capacitativecoupling 63 to the flip-flop circuit 47, thereby removing power from theplaten solenoid 23 so that the platen 25 returns to the FIG. 1condition. The system has now completed a complete cycle and willstand-by until closure of switch 57 starts another measuring cycle.

The sequence of mechanical actions can be summarized as follows:

(1) Valve 17 opens.

(2) Sack 24 is filled.

(3) Valve 17 closes.

(4) Platen 25 collapses sack 24, forcing air into syringe 26.

(5) After sufficient time for reading the measurement, as determined bythe RC constant of the circuit 60, the valve 42 opens and the syringepiston 29 is pulled down.

(6) The piston is latched in its down position and the valve 42 closed.

(7) The platen is retracted but the sack does not expand since allaccess ports as at 29, 42 and 18 are closed.

A more retailed description of the electrical functioning correspondingto the above-described mechanical sequence is set down below.

Operation The trigger 15, amplifier 50, and Schmitt trigger 51 produce anegative pulse each time the infant begins inspiration. These pulses arerouted by the emitter follower 53 to the And gate 54 but go no furtheruntil the read switch 57 is depressed. Actuation of the read switch 57by the operator of the apparatus causes the fiip-fiop 48 to produce aninput to the And gate 54. Upon the first coincidence at the gate 54 ofthis input from the flip-flop 48 and the pulse from the emitter follower53, the flip-flop 49 produces an input to the power amplifier 55 whichcauses rotary valve 17 to open the access to the collection chamber 22.Upon the second coincidence of a pulse from the emitter follower 53 andthe input from flip-flop 48, which has remained present at the And gate54 since its initial appearance, the fiipfiop 45 returns to its startposition. This simultanously causes flip-flop 48 to return to its startposition, preventing further pulses from the emitter follower 53 frompassing through the And gate 54, and removes the input to the poweramplifier 55. This allows the rotary valve 17 to close. Hence, the airexhaled. between the two inspirations has entered the collection chamber22 and is now held there.

The return of the flip-flop 49 to its initial position additionallycauses the flip-flop 47 to change states. When the flip-flop 47 changesstates, power is'supplied to an electromagnetic spring-loaded latch 65that holds the pulldown arm 41 firmly on the syringe piston 29' and aninput is presented to power amplifier 59. The output of the amplifier 59is power to solenoid 23 which pulls the platen 25 against the collectionsack 24 to force the trapped air into the syringe 26 for measurement.

As the platen 25 reaches its final position, it actuates switch 46. Thesignal produced by the closing of switch 46 is delayed by the RC network60' and Schmitt trigger 61. The time that this signal is delayed is thetime in which the measurement made by the apparatus 'is displayed. Theoutput produced by the Schmitt trigger 61 is the input to the poweramplifier 62. This power amplifier energizes the exhaust valve solenoid43' which opens the valve 42 and communicates the collection andmeasurement chambers 24 and 26 to the atmosphere.- This power amplifieralso energizes the pulldown solenoid 43, which returns the pulldown arm41 and syringe piston 29 to their original positions. Hence, the airthat was once held in the system is forced out into the atmosphere. Thereturn of the pulldown arm 41 to its reset position also actuatesswitches 44 and 45. Actuation of switch 45 interrupts power to thepulldown solenoid 43 and exhaust valve 43'. Actuation of switch 44generates a pulse that returns flip-flop 47 to its original position.Hence, the platen 25 is released, and the electromagnet spring-loadedlatch 65 catches the pulldown arm so that the apparatus is at stand-by.

While in the foregoing specification a detailed description of anembodiment of the invention has been set down for the purpose ofexplanation thereof, many variations in the details herein given may bemade by those skilled in the art without departing from the spirit andscope of the invention.

We claim:

1. In respiratory volume measuring apparatus, a thin inelasticcollapsible sack, volumetric measuring means, a conduit adapted to becoupled at one end thereof to a patient whose breath volume is to bemeasured, the other end of said conduit being coupled to saidcollapsible sack, valve means interposed in said conduit, a secondconduit coupling said sack to said volumetric measuring means, valvemeans operably associated with said second conduit, andelectromechanical collapsing means for collapsing said sack to expel agiven breath volume therefrom into said volumetric measuring means.

2. The structure of claim 1 in which said collapsing means includes abase having a generally planar surface on which said sack is supportedand a planar surfaceequipped platen arranged to move into juxtapositionwith said base, said collapsing means including an electrical circuitfor maintainingsaid platen in juxtaposition relative to said base untilafter said given breath volume has been expelled from said apparatusthrough said second conduit valve means and said second valve means isclosed whereby said platen is movable away from said base withoutinducing expansion of said sack.

3. The structure of claim 2 in which said volumetric measuring meansincludes a positive displacement device and electromechanical means forreturning said device to a condition of no displacement prior to movingsaid platen away from said base.

4. In a respiratory volume measuring apparatus, a conduit adapted to becoupled at one end thereof to a patient whose breath volume is to bemeasured, the other end of said conduit being coupled to a collapsiblesack, valve means interposed in said conduit, a second conduit couplingsaid sack to volumetric measuring means, valve means operably associatedwith said second conduit, means for collapsing said sack, means forapplying collapsing force to said sack to expel a given breath volumetherefrom into said volumetric measuring means, and means for purgingsaid volumetric measuring means of said given breath volume prior toremoving the collapsing force from said sack.

5. The structure of claim 4 in which means including a time delaycircuit is operably associated with said applying means and purgingmeans for delaying the opera tion of said purging means a discrete timefollowing the application of said collapsing force.

6. A respiratory volume measuring device, comprising a face mask, a pairof conduits coupled to said mask and providing inhalation and exhalationpaths, means in said inhalation conduit responsive to inhalation of air,valve means in said exhalation conduit adapted to selectively passexhaled air to atmosphere and to volume-measuring means,volume-measuring means coupled to said exhalation conduit and equippedwith means for purging said volume-measuring means of an exhaled breath,and means including a flip-flop circuit interconnecting said responsivemeans, valve means, volume-measuring means and purging means for firstpositioning said valve means to pass an exhaled breath to saidvolume-measuring means in response to a signal from said responsivemeans, secondly for positioning said valve means to pass subsequentexhaled breaths to atmosphere in response to signals from saidresponsive means until said purging means purges said volume-measuringmeans.

7. The structure of claim 6 in which said flip-flop-including means alsoincludes time delay means providing time to visually present the valueof the breath volume measured by said volume-measuring means, and meansoperably associated with said volume-measuring means for visuallypresenting the value of exhaled breath.

the volume of said 8. The structure of claim 6 in which saidflip-flop-including means includes a second flip-flop circuit coupled toa manually-operable switch, said second flip-flop and said responsivemeans being coupled to an and gate, said and gate being coupled to thefirst-mentioned flipflop for actuating said valve means,volume-measuring means and purging means in timed sequence uponsimultaneous signals from said second flip-flop and responsive means.

9. The structure of claim 6 in which said volumemeasuring means includesa positive displacement device, and solenoid means in said purging meansresponsive to one condition of said flip-flop for placing said device ina position of no displacement.

10. Apparatus for measuring the exhaled breath volume of infants,comprising a nose mask adapted to be secured to an infants face, aninhalation conduit and an exhalation conduit coupled to said mask andequipped with check valve means, a two-position valve in said exhalationconduit adapted to selectively couple said mask to atmosphere and to abreath collection element, a breath collection element coupled to saidexhalation conduit and including a base supporting a collapsible sack, aplaten operably associated with said base for collapsing said sack,means in said inhalation conduit responsive to inhalation forpositioning said valve in a first position to pass the subsequentexhaled breath to said sack, means including flip-flop circuits couplingsaid responsive means and valve for first positioning the same andthereafter for positioning said valve in a second position to pass thenext subsequent exhaled breath to atmosphere, and an exhaustvalve-equipped positive displacement volume-measuring device coupled tosaid sack, said flip-flop circuits being also coupled to said device andelement for sequentially actuating said platen to collapse said sack,actuating said device to a condition of no displacement while openingsaid exhaust valve, closing said exhaust valve, and actuating saidplaten to remove collapsing force from said sack.

References Cited by the Examiner UNITED STATES PATENTS 9/1885 McDonnell128--2.08 9/1961 Shipley 128-2. 08

RICHARD A. GAUDET, Primary Examiner. SIMON BRODER, Examiner,

1. IN RESPIRATORY VOLUME MEASURING APPARATUS, A THIN INELASTICCOLLAPSIBLE SACK, VOLUMETRIC MEASURING MEANS, A CONDUIT ADAPTED TO BECOUPLED AT ONE END THEREOF TO A PATIENT WHOSE BREATH VOLUME IS TO BEMEASURED, THE OTHER END OF SAID CONDUIT BEING COUPLED TO SAIDCOLLAPSIBLE SACK, VALVE MEANS INTERPOSED IN SAID CONDUIT, A SECONDCONDUIT COUPLING SAID SACK TO SAID VOLUMETRIC MEASURING MEANS, VALVEMEANS OPERABLY ASSOCIATED WITH SAID SECOND CONDUIT, ANDELECTROMECHANICAL COLLAPSING MEANS FOR COLLAPSING SAID SACK TO EXPEL AGIVEN BREATH VOLUME THEREFROM INTO SAID VOLUMETRIC MEASURING MEANS.